#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int size = 0, doll = 20, num = 0;
	while (doll > 2)
	{
		size = size+doll / 2;
		doll = doll / 2;
	}
	printf("%d\n", size+20);
	return 0;
}